import java.util.HashSet;

public class work1 {
    public boolean isUnique(String astr) {
        HashSet<Character> set=new HashSet<>();
        for (int i = 0; i <astr.length() ; i++) {
            char s=astr.charAt(i);
            if(set.contains(s))return false;
            set.add(s);
        }
        return true;
    }
}
